A 52-year-old female presented with a progressively enlarging vulvar mass. Pathological evaluation revealed a high-grade vulvar leiomyosarcoma. Immunohistochemical and ultrastructural studies were performed to support the diagnosis. In an effort to better understand the biology of this tumor additional immunohistochemical studies for the protein product of p53 tumor suppressor gene and estrogen receptor expression by tumor cells, as well as the type of immune cells infiltrating the tumor were performed. Tumor cells showed an overexpression of p53 protein and were estrogen receptor-positive. Macrophages and T and B lymphocytes infiltrated the tumor in moderate numbers with occasional lymphoid aggregate formation. This study is the first attempt to better understand the biology of these tumors.